However, the companies didn’t confirm the acquisition until just now. Lithium CEO Rob Tarkoff said that he doesn’t see the deal as just an acquisition, but as “redefining” what his company is about. Klout co-founder and CEO Joe Fernandez is joining Lithium as the senior vice president and general manager of the Klout business.

Lithium offers tools for companies to build online communities for their customers. It raised $50 million last fall in what it said was pre-IPO mezzanine financing.

Klout, meanwhile, has raised more than $40 million from investors, including Kleiner Perkins Caufield & Byers, Mayfield Fund, ff Venture Capital, Microsoft, and CrunchFund (which, like TechCrunch, was founded by Michael Arrington). It’s best known (and sometimes criticized) for its score of users’ influence on social media. It recently relaunched its website, adding content sharing recommendations which could potentially help users improve their score.

Fernandez said that with the acquisition, Klout will be able to incorporate activity and influence on Lithium brand communities into its score.

“We will become the company that builds the definitive consumer product in brand profile,” Tarkoff added, with a Klout-type score at the heart of that product. He described the combination of the two companies as “a perfect marriage” between the “richness” of Lithium’s communities and the “reach” of Klout.

Apparently users will get their first peek at how the two companies work together with new products unveiled at Lithium’s LiNC conference in May.

Lithium is not disclosing the price of the acquisition. Tarkoff did say that it was a stock deal and that “if the reports on the value are true, that makes Lithium a very valuable company and I’m very happy about that.”

I want you to know that our mission has not changed — Lithium shares our passion for empowering every person to understand and maximize their impact online. Klout will continue helping people be great online. You will still be able to get insights about your social media performance, find new content to share, and be rewarded with Perks on both Klout.com and our mobile app.

Fernandez concluded the press conference by saying, “If Lithium was a stodgy enterprise company, this wouldn’t have happened.”